Hermetically sealed adjustment for high voltage potentiometer

ABSTRACT

The disclosure relates to a potentiometer for use in high voltage systems of the order of 8 kilovolts wherein the resistance of the potentiometer is adjustable externally of a can containing the potentiometer. The potentiometer is electrically insulated from the externally extending adjusting screw and is hermetically sealed within the can. The adjustment of potentiometer resistance is provided by connecting an adjusting screw which extends through a housing to a threaded rod which is secured to a metal bellows which is sealed in the internal housing within the can to hermetically seal the adjusting screw from the housing interior portion. The threaded rod is coupled via an insulating coupler or spacer to the slide rod of the potentiometer whereby axial movement of the threaded rod moves the slide rod and thereby controls the resistance of the potentiometer. The potentiometer is mounted in the housing and insulated therefrom by insulating spacers, the housing and can being filled with oil.

United States Patent Dorwart, Jr. et al.

[ Jan. 28, 1975 l l HERMETICALLY SEALED ADJUSTMENT FOR HIGH VOLTAGEPOTENTIOMETER [75] Inventors: Charles Edward Dorwart, ,lr.,

Columbia; Meade Goodman Bierly; Charles Nelson Fendrich, .lr., both ofElizabethtown; John Thomas Roland, Manhcim, all of Pa.

[73] Assignee: AMP Incorporated, Harrisburg, Pa.

[22] Filed: Nov. 26, 1973 [21] Appl. No.: 419,168

{52] U.S. (fl. 338/164 I51] Int. Cl. H0lc 5/02, F16j 15/50 {58] Field ofSearch 74/182; 338/164, 231

[56] References Cited UNITED STATES PATENTS 1,478,815 12/1923 Blauvclt H74/182 X 3,187,289 6/l965 Rolwes 338/164 3,248,678 4/1966 Remus 338/1643,373,395 3/1968 Sargent 338/164 I 3,441,894 4/1969 Yamamoto et al.338/231 Primary Examiner-J. V. Truhe Assistant ExaminerKenneth HairstonAttorney, Agent, or Firm-Gerald K. Kita [57] ABSTRACT The disclosurerelates to a potentiometer for use in high voltage systems of the orderof 8 kilovolts wherein the resistance of the potentiometer is adjustableexternally of a can containing the potentiometer. The potentiometer iselectrically insulated from the externally extending adjusting screw andis hermetically sealed within the can. The adjustment of potentiometerresistance is provided by connecting an adjusting screw which extendsthrough a housing to a threaded rod which is secured to a metal bellowswhich is sealed in the internal housing within the can to hermeticallyseal the adjusting screw from the housing interior portion. The threadedrod is coupled via an insulating coupler or spacer to the slide rod ofthe potentiometer whereby axial movement of the threaded rod moves theslide rod and thereby controls the resistance of the potentiometer. Thepotentiometer is mounted in the housing and insulated therefrom byinsulating spacers, the housing and can being filled with oil.

8 Claims, 2 Drawing Figures Patented Jan. 28, 1975 HERMETICALLY SEALEDADJUSTMENT FOR HIGH VOLTAGE POTENTIOMETER This invention relates to ahermetically sealed high voltage potentiometer which is adjustableexternally of the device and more particularly, to such a potentiometerwherein rotary motion external of the housing containing thepotentiometer is converted to a linear motion and transmitted through ametal bellows and electrically insulating coupler to a linear positionpotentiometer.

High voltage potentiometers for use in the 8 kilovolt area have beenknown to the prior art. One such type of prior art potentiometer hasbeen hermetically sealed within an oil filled can, adjustment of thepotentiometer taking place only by breaking the hermetic seal. Anothertype of prior art potentiometer has been positioned externally of thecan containing the high voltage terminals. However, it is stillnecessary to provide a high voltage interface connector to thepotentiometer and, furthermore, since high voltage is applied across thepotentiometer, the external positioning thereof presents a substantialsafety hazard.

In accordance with the present invention, there is provided apotentiometer for use in high voltage systems of the order of 8kilovolts wherein the resistance of the potentiometer is adjustableexternally of a can containing the potentiometer. The potentiometer iselectrically insulated from the externally extending adjustingscrew andis hermetically sealed within the can. The adjustment of potentiometerresistance is provided by connecting an adjusting screw which extendsthrough a housing to a threaded rod which is secured to a metal bellowswhich is sealed in the internal housing within the can to hermeticallyseal the adjusting screw from the housing interior portion. The threadedrod is coupled via an insulating coupler or spacer to the slide rod ofthe potentiometer whereby axial movement of the threaded rod moves theslide rod and thereby controls the resistance of the potentiometer. Thepotentiometer is mounted in the housing and insulated therefrom byinsulating spacers, the housing and can being filled with oil.

It is therefore an objectof this invention to provide a high voltage,potentiometer which is adjustable externally of a hermetically sealedhousing without breaking the seal.

It is a further object of this invention to providea high voltagepotentiometer wherein the resistance is adjusted by converting a rotarymotion to a linear motion'transmitted through an electricallyinsulatingcoupling to a linear position potentiometer;

It is a, still further object of this invention toprovide a high,voltage, potentiometer positioned within a hermetically sealed housingwhich is adjustable externally of the housing.

The above objects and still further objects of the invention willimmediately become apparent to those skilled in the art afterconsideration of the following preferred embodiment thereof, .which isprovided by way of example and not by way of limitation, wherein: FIG. 1is a partially cut away view in elevation of the high voltagepotentiometer in accordance with the present invention; and.

FIG. 2 is a cross sectional view of a portion of the potentiometer ofFIG. 1.

Referring now to the Figures, there is shown the high voltagehermetically sealed potentiometer in accordance with the presentinvention. The potentiometer device includes an external metal can [ofan electrically conductive material such as aluminum having a housing 3therein of an electrically insulating material such as a glass epoxy.The can 1 and housing 3 have one common wall over which is positioned ametal plate 5 which is soldered to the can with solder 7. An adjustmentscrew 9 passes through a locking ring 11 which is positioned on theplate 5, the screw 9 passing through an aperture in the plate into thehousing 3 and threadedly engaging a threaded rod 13 within the housing.A metal bellows 15 is soldered to the threaded rod with solder 17 and tothe side wall of the housing around the screw 9 to hermetically seal thescrew from the interior of the housing. The bellows 15 is preferablyformed from brass. The threaded rod is secured within a spacer orcoupler 19 which is formed from an electrically insulating material suchas a'glass epoxy. The spacer 19 includes grooves 21 to provide a largertracking distance for any discharge from the high voltage components. Aslide rod 23 which is an externally extending part of the self-containedpotentiometer 25 is secured in the spacer l9 and is movable along theaxis of the potentiometer 25 to adjust the resistance value thereof. Thepotentiometer is electrically insulatingly mounted within the housing 3by means of spacers 27 coupling the potentiometer to the housing wall.The

spacers 27 are preferably formed from a glass epoxy material. Thehousing 3 and can 1 are filled with oil in well known manner the housing3 opening into the can 1 at its leftmost end as shown. Terminals 31, 33and 35 are the three standard potentiometer output terminals which wouldbe coupled to an external device in standard circuit operation.

The potentiometer 25' is adjusted externally of the can 1 by rotatingthe screw 9 by means of rotating a screw driver in the slot 29. Thisrotation will cause the rod 13 to move axially due to threading thereofinto or out of the screw 9. The hermetic seal is maintained duringthis'movement by expansion and contraction of the bellows 15. Thecoupler or spacer 19 moves with rod 13 and therefore causes the rod 23to move in the same manner to provide an adjustment of the potentiometerIt can be seen that the adjustment takes place with the screw 9'alwayselectrically insulated from the potentiometer 25, this taking placewithout the necessity of breaking the hermetic seal.

Though the invention has been described with respect to aspecific'preferred embodiment thereof, many variations and modificationswill immediately become apparent to those skilled in the art. It istherefore the intention that the claims be interpreted as broadly aspossible in view of the prior art to include all such variations andmodifications.

What is claimed is:

1. An externally adjustable hermetically sealed high voltagepotentiometer system comprising,

an-electrically insulating hermetically sealed housing,

a potentiometer in the form of a self-contained unit mounted on aninterior wall of the housing adjacent one end thereof,

a linearly movable member for varying the resistance of thepotentiometer slidably supported on the potentiometer unit andprojecting from the unit into the housing, rotatable means extendingthrough the opposite end wall of the housing with its inner endterminating short of the linearly movable member, insulating couplingmeans secured to the linearly movable member and provided with meanscooperating with the inner end of the rotatable means upon rotationthereof to move the linearly movable member, and expandable meanssurrounding said rotatable means and secured to the other end wall aboutthe rotatable means and to the cooperating means hermetically sealingsaid rotatable means from the interior of the housing. 2. Apotentiometer system as set forth in claim 1 wherein said housing isfilled with oil and further including a metal can surrounding saidhousing.

3. A potentiometer system as set forth in claim 1 wherein the inner endof said rotatable means and the means cooperating therewith compriseinterfitting wherein said expandable means comprises a bellows.

1. An externally adjustable hermetically sealed high voltagepotentiometer systeM comprising, an electrically insulating hermeticallysealed housing, a potentiometer in the form of a self-contained unitmounted on an interior wall of the housing adjacent one end thereof, alinearly movable member for varying the resistance of the potentiometerslidably supported on the potentiometer unit and projecting from theunit into the housing, rotatable means extending through the oppositeend wall of the housing with its inner end terminating short of thelinearly movable member, insulating coupling means secured to thelinearly movable member and provided with means cooperating with theinner end of the rotatable means upon rotation thereof to move thelinearly movable member, and expandable means surrounding said rotatablemeans and secured to the other end wall about the rotatable means and tothe cooperating means hermetically sealing said rotatable means from theinterior of the housing.
 2. A potentiometer system as set forth in claim1 wherein said housing is filled with oil and further including a metalcan surrounding said housing.
 3. A potentiometer system as set forth inclaim 1 wherein the inner end of said rotatable means and the meanscooperating therewith comprise interfitting screw threads.
 4. Apotentiometer system as set forth in claim 2, wherein the inner end ofsaid rotatable means and the means cooperating therewith compriseinterfitting screw threads.
 5. A potentiometer system as set forth inclaim 1 wherein said expandable means comprises a bellows.
 6. Apotentiometer system as set forth in claim 2 wherein said expandablemeans comprises a bellows.
 7. A potentiometer system as set forth inclaim 3 wherein said expandable means comprises a bellows.
 8. Apotentiometer system as set forth in claim 4 wherein said expandablemeans comprises a bellows.